Field of the Invention
The invention relates to a sheet conveyor for a delivery of a sheet-fed printing press, having at least one operatively revolving gripper bar guidable in a transport direction along a sheet guiding surface, the bar being provided with grippers having gripper fingers pivotable in a gripper cycle for gripping a gripper edge region of a sheet, the edge region being oriented crosswise to the conveying direction, and the sheet being conveyable one at a time by the gripper bar, and also including a front spoiler for shielding an intermediate space located between the gripper bar and the sheet guiding surface. The invention also relates to a delivery equipped with a sheet conveyor, in a sheet-fed printing press.
A sheet conveyor of this general type has become known heretofore, for example, from the published German Patent Document DE 33 08 907 A1, wherein a front spoiler is disposed so that an end thereof facing towards a sheet guiding surface is located relatively close to the free ends of a gripper finger. This is necessary in the case of heretofore known sheet conveyors, for the purpose of preventing a collision between a sheet-guiding cylinder and the front spoiler, when sheets are taken over by the grippers from that sheet-guiding cylinder.
The gripper fingers are pivotable about an axis, located downline from the free ends of the gripper fingers, as viewed in the sheet conveying direction, and disposed in the gripper bar. Consequently, the front spoiler, beginning at the end thereof facing towards the sheet guiding surface, has at least a tendency to rise in an inclined manner, when compared to a normal to the sheet guiding surface, as viewed downline in the sheet conveying direction. With this configuration, the front spoiler acts as an air scoop that, during operation, pushes a turbulent flow ahead of it.
A flowing under of the sheets guided past the sheet guiding surface by the grippers is indeed largely prevented with the heretofore known sheet conveyor, particularly if the front spoiler is formed of elastic material, in which case contact between the sheet guiding surface and the end of the front spoiler facing towards it can be permitted. The turbulent flow pushed in front of the front spoiler, however, is deleterious particularly to the trailing region of a respectively leading sheet. Precisely for this region, however, there is a need for flutter-free travel, to ensure a secure contact of this region with a sheet brake, and thus to permit a sheet, braked to a deposition speed and then released by the sheet brake, as it is lowered onto a sheet pile from a trailing gripper bar and a trailing sheet brought by that gripper bar to the sheet brake, to be transferred in a contact-free overlapping manner.